1. Field of the Invention
The present invention relates to a coordinate input apparatus which optically detects a coordinate position input to a coordinate input surface by a pointer such as a finger in order to input or select information. Particularly, the present invention relates to a detachable portable coordinate input apparatus.
2. Description of the Related Art
As such coordinate input apparatuses, various types of coordinate input apparatuses (touch panels and digitizers) have conventionally been proposed and commercialized. For example, a touch panel capable of easily operating a terminal such as a PC (Personal Computer) by touching the screen with a finger without using a special tool or the like is widely used.
Coordinate input methods range from a method using a resistive film to a method using an ultrasonic wave. As a method using light, there is known a method (light shielding method) of arranging a retroreflecting member outside a coordinate input surface, reflecting light from a light projecting unit by the retroreflecting member, and detecting the light amount distribution by a light receiving unit (see, for example, U.S. Pat. No. 4,507,557 and Japanese Patent Laid-Open No. 2004-272353). This method detects the direction of a light shielding portion (region) where light is cut off with a finger or the like in the coordinate input region, and determines the coordinates of the light shielding position, that is, coordinate input position.
FIG. 16 shows an arrangement as an example of generalizing the arrangement disclosed in the specification of U.S. Pat. No. 4,507,557. FIG. 16 shows sensor units 2L and 2R which are arranged at two ends of a coordinate input surface, and an effective coordinate input region 5 serving as a coordinate input surface used to input coordinates. A retroreflecting member 4 is arranged on three sides around the effective coordinate input region 5 to retroreflect incident light in the incident direction.
Each of the sensor units 2L and 2R includes a light projecting unit and light receiving unit (not shown). The light projecting unit projects light, which spreads in a fan-like shape almost parallelly to the input surface of the effective coordinate input region 5. The retroreflecting member 4 retroreflects the light, and the light receiving unit receives the return light. The coordinate input apparatus can calculate a touch position P input to the effective coordinate input region 5 based on the light shielding directions (light shielding angles θL and θR) of beams detected by the two sensor units 2L and 2R, and the distance between these sensor units.
As shown in FIG. 16, the field ranges of the sensor units 2L and 2R are symmetrically set by using the optical axis directions of the sensor units 2L and 2R as symmetry lines. In a coordinate input apparatus of this type using the lens optical system, if an angle formed with the optical axis increases, the optical performance always degrades under the influence of aberration. Employing a centered optical system can implement a higher-performance apparatus.
In FIG. 16, an arithmetic control circuit 3 controls the sensor units 2L and 2R, processes acquired output signals from the sensor units 2L and 2R, and outputs the processing result to an external apparatus.
Japanese Patent Laid-Open No. 2004-272353 exemplifies the detailed arrangements of the light projecting unit and light receiving unit of the sensor unit in the light shielding coordinate input apparatus disclosed in the specification of U.S. Pat. No. 4,507,557.
Further, Japanese Patent Laid-Open No. 2001-43021 discloses an arrangement which controls lighting of light projecting units in respective sensor units. More specifically, in Japanese Patent Laid-Open No. 2001-43021, it is controlled to alternately emit light from the light projecting units of the sensor units in order to prevent reception of light emitted by the light projecting unit of one sensor unit as disturbance light by the light receiving unit of the other sensor unit.
Further, Japanese Patent No. 4118664 discloses an arrangement in which a plurality of sensor units are arranged on two facing sides of an effective coordinate input region, and form a gap between a retroreflecting member and a coordinate input surface.
Integrating a coordinate input apparatus of this type with a display apparatus makes it possible to control the display state by touching the display screen of the display apparatus, or display the locus of a touch position as handwriting as in the relationship between paper and a pencil.
As the display apparatus, flat panel displays and front projectors of various types such as a liquid crystal display are known. For the flat panel display, the above-mentioned operational environment can be implemented by superimposing a coordinate input apparatus on it. A mobile device such as a smartphone is a typical example of this. Along with upsizing of flat panel displays, it is becoming popular to combine the flat panel display with a large-size touch panel and introduce it into, for example, the digital signage field.
For the front projector capable of a large-size display, a position detection unit is assembled into a screen board or the like serving as its projection surface, and an image is projected onto the screen board. The size of the coordinate input apparatus depends on that of the screen board serving as a touch operation surface, and the apparatus becomes relatively large. In general, therefore, a stand for moving the screen board is attached to the screen board, or the screen board is fixed to the wall and used. A larger-size front projector exponentially raises the sales price, seriously inhibiting the spread of a large-size coordinate input apparatus and an application using it.
In the light shielding coordinate input apparatus shown in FIG. 16, the sensor units 2, arithmetic control circuit 3, and retroreflecting member 4 are main components and attached to the screen board. Even if the apparatus becomes large, the arrangement of the main components remains unchanged, and the cost of the material of the screen board occupies most part of the cost rise caused by upsizing.
A user interface operated by touching the display screen of a display apparatus is intuitive and usable by everyone and has gone mainstream in mobile devices now. Such an operation is requested of even an apparatus having a larger display screen.
Detailed applications of a large screen are mainly requested from markets such as ICT education in the classroom and digital signage as a presentation function at a meeting and a whiteboard function. To meet this demand, the introduction cost for implementing the operational environment needs to be greatly reduced.
In most current meeting rooms and classrooms, whiteboards and front projectors have already been introduced as equipment. The present invention has as its object to provide an operational environment capable of a touch operation at low cost even for a large screen by effectively using such apparatuses already purchased by the user.
As described above, the main building components of the light shielding coordinate input apparatus are at least two sensor units 2 which detect directions in which the optical path is cut off by a touch operation, the arithmetic control circuit 3, and the retroreflecting member 4. If these main building components can be attached to, for example, a whiteboard at predetermined positions and sizes, a touch position on the whiteboard can be detected. Using an existing whiteboard as the screen board can omit, from indispensable building components, the screen board itself which occupies most of the cost. This can greatly suppress the product price and provide a touch operation environment at low cost even for a large screen.
The position detection principle of the light shielding coordinate input apparatus geometrically calculates a touch position based on light shielding directions (=angles) of the touch position output from at least two sensor units, and distance information between these sensor units. To detect a touch position at high accuracy, the sensor units need to be positioned and attached at high accuracy. It is more preferable that the user can easily attach these sensor units.
In contrast, even rough positioning and attachment of the sensor units by the user can implement the following usage if high-accuracy touch position detection is possible. More specifically, only the main building components of the light shielding coordinate input apparatus are carried, and used by easily attaching them within a short time to a whiteboard installed in a meeting room where a meeting is held. After the end of the meeting, the main building components are detached and carried back, or carried to another meeting room and used there. In short, a detachable portable coordinate input apparatus can be operated by “everybody” at any time “anywhere” “easily”. The number of building components of a product itself for implementing this is preferably small. Further, the product is compact and lightweight for portability.
Since the main building components can be attached and detached, they can be attached to, for example, an already purchased whiteboard by using magnets. Using the whiteboard as the projection surface can provide an input/output integrated touch operation environment. In general, whiteboards of various sizes are commercially available. By using a larger-size whiteboard, an image can be projected onto a larger display surface, needless to say. It is preferable that the main building components can be set in accordance with various sizes of whiteboards installed in meeting rooms and can detect a touch position at high accuracy.
The conventional optical coordinate input apparatus adopts a scheme of detecting a touch position in accordance with the principle of triangulation based on pieces of angle information output from at least two angle detection sensors, and the distance between the two angle detection sensors. Therefore, to use the conventional apparatus as a coordinate input apparatus, the distance between the two angle detection sensors must be known.
However, whiteboards owned by the user as projection surfaces have various sizes, so display images corresponding to these sizes are projected. As shown in FIG. 16, two angle detection sensors are arranged near the corners of a display region, but the regions where these sensors are set must be ensured on the whiteboards.
It is therefore preferable to appropriately change the distance between the angle detection sensors in accordance with the shape or size of the whiteboard or projection surface owned by the user. To detect a touch position, the distance between the sensors set by the user must be measured using some kind of method, thus requiring, for example, a distance measurement sensor for this measurement. This inevitably increases the cost.